/Engine/Source/Runtime/Engine/Public/AudioStreamingCache.h
Places chunk in cache, or puts this chunk back at the top of the cache if it's already loaded. Returns the static lookup ID of the chunk in the cache on success, or InvalidAudioStreamCacheLookupID on failiure.
uint64 AddOrTouchChunk ( const [FChunkKey](API\Runtime\Engine\FAudioChunkCache\FChunkKey) & InKey, const [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [FSoundWaveData](API\Runtime\Engine\Sound\FSoundWaveData) > & InSoundWavePtr, [TFunction](API\Runtime\Core\GenericPlatform\TFunction)< void(EAudioChunkLoadResult) > OnLoadCompleted, [ENamedThreads::Type](API\Runtime\Core\Async\ENamedThreads__Type) CallbackThread, bool bNeededForPlayback )